Summary: Mon. Not. R. Astron. Soc. 000, 000{000 (0000) Printed 1 August 2002 (MN L A T E X style le v2.2)
Hydrodynamical simulations of the decay of high-speed
molecular turbulence. I. Dense molecular regions
Georgi Pavlovski, 1? Michael D. Smith, 1 Mordecai-Mark Mac Low, 2
& Alexander Rosen 1
1 Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland, U.K.
2 American Museum of Natural History, Department of Astrophysics, 79th St. at Central Park West, New York, NY 10024-5192, USA
Accepted .... . Received .... ; in original form ....
ABSTRACT
We present the results from three dimensional hydrodynamical simulations of decay-
ing high-speed turbulence in dense molecular clouds. We compare our results, which
include a detailed cooling function, molecular hydrogen chemistry and a limited C and
O chemistry, to those previously obtained for decaying isothermal turbulence.
After an initial phase of shock formation, power-law decay regimes are uncov-
ered, as in the isothermal case. We nd that the turbulence decays faster than in the
isothermal case because the average Mach number remains higher, due to the radiative
cooling. The total thermal energy, initially raised by the introduction of turbulence,
decays only a little slower than the kinetic energy.
We discover that molecule reformation, as the fast turbulence decays, is several
times faster than that predicted for a non-turbulent medium. This is caused by moder-